1. Field of the Invention
The present invention relates to information processing equipment such as workstations and more particularly, to an information transferring system designed to exchange data among different window systems and to display the different window systems on a display screen of a display apparatus.
2. Discussion of the Related Art
Along with the progressive utilization of information processing systems and equipment, such as workstations, the use of multiple window systems on these workstations has become increasingly popular. Multiple window systems are systems constructed to display a plurality of windows on the same display. The use of a multiple window system makes it possible to perform a plurality of processing operations on one display screen as set in correspondence with the individual windows and to perform such operations as the transfer of picture images in an efficient way by the use of a plurality of windows.
For the display of a plurality of windows on the display screen of a display apparatus, the windows are operated by either a single system in some cases or by a plurality of systems in other cases. In the former case, one processing program operates a plurality of windows shown on the display screen, however, in the latter case, a plurality of processing programs operate the respective windows displayed on one display screen.
FIG. 16 illustrates one example of a screen displaying multiple windows operated by a plurality of processing programs. The display screen 11 on the display unit shows a window 12 generated on the display screen by a first window system and another window 13 generated on the display screen by a second window system. Since the first window system and the second window system are different systems, their processing functions will be different between a case where the cursor (not illustrated in the Figure) is present, for example, inside the window 12 and another case in which the cursor is present inside the other window 13.
Even with a multiple window system like the one described, users demand improvements in the manner in which the systems operate with emphasis on the ease and efficiency in the preparation of documents. For example, users require a multiple window system capable of copying or moving the data of a document, a line drawing, or the like, inside one window 12 to the field inside the other window 13.
In the latter case described above, however, the window systems themselves are different and it is usually the case that such different processing systems have many differences including, for example, differences in character codes, differences in the control code for the display of characters, and differences in the process of producing line drawings. Therefore, unlike the case of the transfer of data in a multiple window system operated by a single processing system, where each of a plurality of processing programs operates the display of a window on the display screen simultaneously users require the capacity to perform exchange data among such different window systems.
Consequently, an information processing system capable of operating a plurality of window systems has been provided with a data storing area called a "clipboard". Thus, for the transfer of data from one window system to a different window system, the data to be transferred is first written to a clipboard by the first window system and subsequently the second window system may read out the data stored on this clipboard. This process allows for the exchange of data between different window systems.
Disadvantageously, in the ordinary case, only one such clipboard is provided in the area of the window systems. Accordingly, in case it is designed to put different window systems into operation at the same time, such individual window systems will independently control the clipboard. Presently, the individual window systems execute the operation of a clipboard, specifying some addresses in the memory area from time to time, depending on the data to be processed on each particular occasion For this reason, even if a given window system has stored data in the memory medium on a clipboard at addresses starting with the address a, another window system is not able to gain any knowledge of this address a, so that it is virtually impossible to perform the exchanges of data between different window operating systems.
The above description details the exchange of data by a process using a clipboard, but it is noted that problems have also been found with the exchange of data by a process using selection. The difference between a clipboard and a selection process is described below.
When using a clipboard, the processing system which transfers data specifies the clipboard as a site for the transfer and retrieval of the data and stores the data on the specified clipboard. The processing system which requires the data searches the clipboard and retrieves the data from it.
However, when using the selection process, the processing system which requires data accesses to the processing system which maintains the data and requests the data. The system which maintains the data searches for the required data and stores the data found by such a search in a prescribed storing location, via which the data is delivered to the processing system requesting the data.
When data exchanges are performed by such a selection process between different window systems, even if a window system requiring some data accesses the window system which maintains the data requesting the data, such a request is made by a different system, and the window system which has the requested data cannot understand the request (or demand) because the two systems are different in their data format and so forth. Therefore, it is impossible to exchange data by the use of the protocol called "selection" between different window systems.